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Giardiasis

Giardiasis

Definition

Giardiasis is a common intestinal infection spread by eating contaminated food, drinking contaminated water, or through direct contact with the organism that causes the disease, Giardia lamblia. Giardiasis is found throughout the world and is a common cause of traveller's diarrhea. In the United States it is a growing problem, especially among children in childcare centers.

Description

Giardia is one of the most common intestinal parasites in the world, infecting as much as 20% of the entire population of the earth. It is common in overcrowded developing countries with poor sanitation and a lack of clean water. Recent tests have found Giardia in 7% of all stool samples tested nationwide, indicating that this disease is much more widespread than was originally believed. It has been found not only in humans, but also in wild and domestic animals.

Giardiasis is becoming a growing problem in the United States, where it affects three times more children than adults. In recent years, giardiasis outbreaks have been common among people in schools or daycare centers and at catered affairs and large public picnic areas. Children can easily pass on the infection by touching contaminated toys, changing tables, utensils, or their own feces, and then touching other people. For this reason, infection spreads quickly through a daycare center or institution for the developmentally disabled.

Unfiltered streams or lakes that may be contaminated by human or animal wastes are a common source of infection. Outbreaks can occur among campers and hikers who drink untreated water from mountain streams. While 20 million Americans drink unfiltered city water from streams or rivers, giardiasis outbreaks from tainted city water have been rare. Most of these problems have occurred not due to the absence of filters, but because of malfunctions in city water treatment plants, such as a temporary drop in chlorine levels. It is possible to become infected in a public swimming pool, however, since Giardia can survive in chlorinated water for about 15 minutes. During that time, it is possible for an individual to swallow contaminated pool water and become infected.

Causes and symptoms

Giardiasis is spread by food or water contaminated by the Giardia lamblia protozoan organism found in the human intestinal tract and feces. When the cysts are ingested, the stomach acid degrades the cysts and releases the active parasite into the body. Once within the body, the parasites cling to the lining of the small intestine, reproduce, and are swept into the fecal stream. As the liquid content of the bowel dries up, the parasites form cysts, which are then passed in the feces. Once excreted, the cysts can survive in water for more than three months. The parasite is spread further by direct fecal-oral contamination, such as can occur if food is prepared without adequate hand-washing, or by ingesting the cysts in water or food.

Giardiasis is not fatal, and about two-thirds of infected people exhibit no symptoms. Symptoms will not occur until between one and two weeks after infection. When present, symptoms include explosive, watery diarrhea that can last for a week or more and, in chronic cases, may persist for months. Because the infection interferes with the body's ability to absorb fats from the intestinal tract, the stool is filled with fat. Other symptoms include foul-smelling and greasy feces, stomach pains, gas and bloating, loss of appetite, nausea and vomiting. In cases in which the infection becomeschronic, lasting for months or years, symptoms might include poor digestion, problems digesting milk, intermittent diarrhea, fatigue, weakness, and significant weight loss.

Diagnosis

Diagnosis can be difficult because it can be easy to overlook the presence of the giardia cysts during a routine inspection of a stool specimen. In the past, the condition has been diagnosed by examining three stool samples for the presence of the parasites. However, because the organism is shed in some stool samples and not others, the infection may not be discovered using this method.

A newer, more accurate method of diagnosing the condition is the enzyme-linked immunosorbent assay (ELISA) that detects cysts and antigen in stool, and is approximately 90% accurate. While slightly more expensive, it only needs to be done once and is therefore less expensive overall than the earlier test.

Treatment

Acute giardiasis can usually be allowed to run its natural course and tends to clear up on its own. Antibiotics are helpful, however, in easing symptoms and preventing the spread of infection. Medications include metronidazole, furazolidone and paromomycin. Healthy carriers with no symptoms do not need antibiotic treatment. If treatment should fail, the patient should wait two weeks and repeat the drug course. Anyone with an impaired immune system (immunocompromised), such as a person with AIDS, may need to be treated with a combination of medications.

Prognosis

Giardiasis is rarely fatal, and when treated promptly, antibiotics usually cure the infection. While most people respond quickly to treatment, some have lingering symptoms and suffer with diarrhea and cramps for long periods, losing weight and not growing well. Those most at-risk for a course like this are the elderly, people with a weakened immune system, malnourished children, and anyone with low stomach acid.

Prevention

The best way to avoid giardiasis is to avoid drinking untreated surface water, especially from mountain streams. The condition also can be minimized by practicing the following preventive measures:

  • thoroughly washing hands before handling food
  • maintaining good personal cleanliness
  • boiling any untreated water for at least three minutes
  • properly disposing of fecal material

Children with severe diarrhea (and others who are unable to control their bowel habits) should be kept at home until the stool returns to normal. If an outbreak occurs in a daycare center, the director should notify the local health department. Some local health departments require a follow-up stool testing to confirm that the person is no longer contagious. People not in high-risk settings can return to their routine activities after recovery.

Resources

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

OTHER

Centers for Disease Control. http://www.cdc.gov/ncidod/EID/eidtext.htm.

International Society of Travel Medicine. http:www.istm.org.

KEY TERMS

Antibody A specific protein produced by the immune system in response to a specific foreign protein or particle called an antigen.

Antigen A substance (usually a protein) identified as foreign by the body's immune system, triggering the release of antibodies as part of the body's defense mechanism.

Enzyme-linked immunosorbent assay (ELISA) A laboratory technique used to detect specific antigens or antibodies. It can be used to diagnose giardiasis.

Giardia lamblia A type of protozoa with a whiplike tail that infects the human intestinal tract, causing giardiasis. The protozoa will not spread to other parts of the body.

Immunocompromised A state in which the immune system is suppressed or not functioning properly.

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"Giardiasis." Gale Encyclopedia of Medicine, 3rd ed.. . Encyclopedia.com. 18 Aug. 2017 <http://www.encyclopedia.com>.

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giardiasis

giardiasis (jēärdī´əsĬs, järdī´əsĬs), infection of the small intestine by a protozoan, Giardia lamblia.Giardia, which was named after Alfred M. Giard, a French biologist, is spread via the fecal-oral route, most commonly by eating food contaminated by the unwashed hands of an infected person or by drinking groundwater polluted by the feces of infected animals such as dogs and beavers (hence the nickname "beaver fever" ). It attaches itself to the walls of the small intestine and there multiplies quickly. About two thirds of infected individuals develop no symptoms. Symptoms, when present, occur one to three days after infection and consist of diarrhea, flatulence, and abdominal cramps, often accompanied by weight loss. In some cases the infection becomes chronic. Giardiasis has traditionally been considered a tropical disease, but it is becoming more common in developed countries, especially among gay men and among groups of very young children in close contact with each other, as in day-care centers before toilet training and proper handwashing techniques have been mastered. Diagnosis is by direct microscopic examination of the stool or by testing for antibodies to the parasite. In most cases no treatment is necessary. The drugs metronidazole, tinidazole, and nitazoxanide are sometimes prescribed.

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Giardiasis

Giardiasis

What Is Giardiasis?

What Are the Signs and Symptoms of Giardiasis?

How Do Doctors Diagnose Giardiasis?

How Do Doctors Treat Giardiasis?

How Do People Prevent Giardiasis?

Resource

Giardiasis is an infection of the small intestine by the Giardia lamblia parasite. It is spread from person to person or by contact with contaminated water or food. Its major symptom is diarrhea.

KEYWORDS

for searching the Internet or other reference sources

Gastrointestinal system

Waterborne diseases

What Is Giardiasis?

Giardiasis (je-ar-DY-a-sis) is a common infection caused by the Giardia Umblia (je-AR-de-a LAM-bli-a) protozoan, which is a one-celled organism that lives as a parasite*. Giardia contamination can occur in any water source, from clear mountain streams to poorly filtered city water supplies. The most common carriers of giardiasis are dogs, beavers, and humans. Giardiasis is easily passed from person to person through poor hygiene.

* parasites
are creatures that live in and feed on the bodies of other organisms. The animal or plant harboring the parasite is called its host.

Giardiasis is found worldwide in both developed and developing countries and in both temperate and tropical climates. In developing nations, infection rates from 20 to 50 percent may occur. In the United States, it is estimated to affect up to 20 percent of the population, with toddlers in diapers at busy day care centers at particular risk.

What Are the Signs and Symptoms of Giardiasis?

It is estimated that more than 50 percent of people with giardiasis have no symptoms or only mild symptoms. When symptoms of giardiasis do occur, they may start gradually or suddenly, usually within one to three weeks after exposure to the parasite. The illness usually begins with frequent watery diarrhea without blood or mucus. Because giardiasis affects the bodys ability to absorb fats and carbohydrates from ingested foods (malabsorption), giardiasis often produces foul-smelling, oily stools that float. Symptoms also may include abdominal cramps, a swollen or large abdomen, excessive gas, nausea and vomiting, loss of appetite, and sometimes a low-grade fever. Persistent symptoms can lead to weight loss and dehydration.

How Do Doctors Diagnose Giardiasis?

Giardiasis is diagnosed by examination of stool samples under a microscope. Doctors look for evidence of trophozoites (tro-fo-ZO-ites), which are active Giardia protozoa inside the body, or for evidence of cysts, which are Giardia surrounded by a protective wall, the form of the protozoan during the resting stage of its life cycle. Detecting Giardia is difficult, so doctors often need to repeat the stool sample tests several times before they can confirm or rule out Giardia infection. Diagnostic tests may sometimes take as long as four or five weeks.

How Do Doctors Treat Giardiasis?

Several drugs are available for treatment of giardiasis, and some of them work well in a single dose. Sometimes a second round of drug treatment is required. There is some controversy among doctors about whether to treat people who carry the parasite but who do not have symptoms of giardiasis. Treatment is sometimes considered because these individuals may transmit the infection to others and may eventually show symptoms themselves.

How Do People Prevent Giardiasis?

There is no vaccine or prophylactic (disease-preventing) drug for giardiasis. Preventing giardiasis depends on maintenance of safe supplies of drinking water, the sanitary disposal of human and animal waste, washing of fruits and vegetables before eating or cooking, and proper hygiene, which includes thorough washing of hands after going to the bathroom and before eating.

The Giardia protozoan can be filtered from water but is otherwise difficult to destroy. It can survive in cold water for as long as two months, and it is resistant to chlorine levels used to purify municipal water supplies. When municipal water supplies have been approved by local health departments, the water may be considered safe to drink. But when camping or traveling, it is important to make sure that drinking water, cooking water, and ice come only from safe sources. Clear cold mountain streams may look safe and inviting but they may also carry the Giardia parasite.

See also

Diarrhea

Gastroenteritis

Resource

The U.S. National Institute of Allergy and Infectious Diseases posts a fact sheet about giardiasis at its website. http://www.niaid.nih.gov/factsheets/GIARDIA.htm

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"Giardiasis." Complete Human Diseases and Conditions. . Retrieved August 18, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/giardiasis

giardiasis

giardiasis (lambliasis) (jy-ar-dy-ă-sis) n. a disease caused by the parasitic protozoan Giardia lamblia in the small intestine. Symptoms include diarrhoea, nausea, bellyache, flatulence, and the passage of pale fatty stools (steatorrhoea). The disease is particularly common in children; it responds well to oral doses of metronidazole.

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giardiasis

giardiasis Intestinal inflammation and diarrhoea caused by infection with the protozoan parasite Giardia lamblia.

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